DIESEL. PROGRESS

Evening Post, Volume CXXII, Issue 22, 25 July 1936, Page 28

DIESEL. PROGRESS

MOTOR-CAR UNITS

ECONOMIC TRAVEL

The rapid progress being made with the development of oil engines for commercial road vehicles in the past eight years, and the steady progress in the adaptation of such engines for motor-car purposes is noted in an article in "The Motor."

The economy of this class of prime mover is due to a combination of two factors. One is the much higher thermal efficiency which results from

the greater coiripression ratio which is practicable when air (instead of a mixture) is compressed. . The second is the fact that practically all over the world oil fuel is cheaper than petrol, up to a ratio of 1 to 6.

Oil-engined cars are now listed by several. makers in America and Germany and Britain is not lagging behind. "The Motor" gives its impression of an English engine recently tested, a 3.35 litre unit mounted in place oi the petrol engine in an American chassis, controls, cooling system, and transmission remaining the same.

"We approached the noise probiem from a viewpoint rather more critical than that of the average private owner, in view of experience with earlier oil-engined cars, which were definitely below petrol-engine standards in point of quiet running and smoothness," states the paper. "It is now fair to say that the noise which the driver and passengers hear is no greater than that heard with many p'etrol-engined cars. Such noise as can be heard, when all the saloon windows are closed, disappears when the speed exceeds 25 m.p.h., and at all speeds up to the maximum (65 m.p.h. by speedometer) there is no sign of what is commonly called "Diesel knock" or other engine noise.

"Response to the accelerator, whether upwards or downwards in the speed range, is just as rapid as with the average four-cylinder petrol engine, and changes of gear, whether travelling fast or slowly, were, we found effected as quickly as on a conventional car.

"Speed is controlled entirely byaccelerator pedal, as in modern petrol-engine practice. Slow running is set by a vacuum governor which, acting upon the fuel-injection pump, cuts down the quantity of fuel injected ' per stroke; the injection timing, which .corresponds to the ignition advance of a petrol engine, is also regulated by the accelerator pedal travel: : ■ •

"The cost of conversion of a car is in the neighbourhood of £180, but it must, of course, be clear that the figure varies somewhat' in accordance with the amount of work done." ■